Exhaust gas purification catalyst, method for purifying exhaust gas, and method for producing exhaust gas purification catalyst

Abstract

An exhaust gas purification catalyst ( 10 ) contains a refractory three-dimensional structure ( 20 ), a second catalyst layer ( 31 ) containing palladium and rhodium, and a first catalyst layer ( 32 ) containing palladium positioned between the refractory three-dimensional structure ( 20 ) and the second catalyst layer ( 31 ), in which the first catalyst layer ( 32 ) or the second catalyst layer ( 31 ) further contains a Zr—Pr composite oxide that is a composite oxide of zirconium and praseodymium. A proportion of a mass of praseodymium oxide contained in the Zr—Pr composite oxide relative to a total mass of zirconium oxide and praseodymium oxide contained in the Zr—Pr composite oxide may be 11% or more and 90% or less.

1 . An exhaust gas purification catalyst comprising:
 a refractory three-dimensional structure;   a second catalyst layer containing palladium and rhodium; and   a first catalyst layer containing palladium positioned between the refractory three-dimensional structure and the second catalyst layer,   wherein the first catalyst layer or the second catalyst layer further contains a Zr—Pr composite oxide that is a composite oxide of zirconium and praseodymium.   
     
     
         2 . The exhaust gas purification catalyst according to  claim 1 , wherein a proportion of mass of praseodymium oxide (in terms of Pr 6 O 11 ) contained in the Zr—Pr composite oxide relative to a total mass of zirconium oxide and praseodymium oxide (in terms of ZrO 2  and Pr 6 O 11 ) contained in the Zr—Pr composite oxide is 11% or more and 90% or less. 
     
     
         3 . The exhaust gas purification catalyst according to  claim 1 , wherein
 an amount of palladium contained in the second catalyst layer is 0.1 g or more and 15.0 g or less per 1 liter of the refractory three-dimensional structure,   an amount of rhodium contained in the second catalyst layer is 0.05 g or more and 5.0 g or less per 1 liter of the refractory three-dimensional structure, and   an amount of palladium contained in the first catalyst layer is 0.5 g or more and 15.0 g or less per 1 liter of the refractory three-dimensional structure.   
     
     
         4 . The exhaust gas purification catalyst according to  claim 1 , wherein an amount of the Zr—Pr composite oxide is 10 g or more and 80 g or less per 1 liter of the refractory three-dimensional structure. 
     
     
         5 . The exhaust gas purification catalyst according to  claim 1 , wherein the amount of the Zr—Pr composite oxide in the first catalyst layer or the second catalyst layer containing the Zr—Pr composite oxide is 5 mass % or more and 50 mass % or less. 
     
     
         6 . The exhaust gas purification catalyst according to  claim 1 , wherein the second catalyst layer contains the Zr—Pr composite oxide. 
     
     
         7 . A method for purifying exhaust gas, comprising using the exhaust gas purification catalyst according to  claim 1 . 
     
     
         8 . A method for producing the exhaust gas purification catalyst according to  claim 1 , comprising:
 a first step of applying a first slurry on a surface of a refractory three-dimensional structure and drying and calcining the applied first slurry to form a first catalyst layer; and   a second step of applying a second slurry on a surface of the first catalyst layer and drying and calcining the applied second slurry to form a second catalyst layer,   wherein   the first slurry contains a palladium compound,   the second slurry contains a palladium compound and a rhodium compound, and   the first slurry or the second slurry further contains a Zr—Pr composite oxide that is a composite oxide of zirconium and praseodymium.